DIY Electric Car Forums banner

1 - 13 of 13 Posts

·
Registered
Joined
·
78 Posts
Discussion Starter #1
I'm a newbie. I have an old Land Rover I'd like to turn into an EV.

I may be able to get hold of a scrap Nissan Leaf. The batteries look easy enough to extract (explained here).

The motor looks powerful enough.

But - my goodness - having read all the relevant threads on here, making the whole system work once removed from the Leaf is way beyond my abilities.

Can I just use the naked motor, the naked cells, and a third party speed controller to wire something simple up?

Thanks very much.
 

·
Registered
Joined
·
4,752 Posts
Can I just use the naked motor, the naked cells, and a third party speed controller to wire something simple up?
In theory you certainly can run the motor with any 3-phase inverter/controller designed to run a synchronous motor at the appropriate voltage, as long at it can connect (perhaps with additional hardware) to whatever Nissan used as a shaft position encoder. Most readily available AC motor controllers are designed for a much lower voltage.

Although I haven't seen anyone stripping a Leaf pack down to the bare cells, stripping it down to the bare modules (of four cells each) and using your own BMS is practical - check out this for an example:
Leaf module based 150V 65Ah battery pack...
 

·
Registered
Joined
·
78 Posts
Discussion Starter #3
In theory you certainly can run the motor with any 3-phase inverter/controller designed to run a synchronous motor at the appropriate voltage, as long at it can connect (perhaps with additional hardware) to whatever Nissan used as a shaft position encoder. Most readily available AC motor controllers are designed for a much lower voltage.

Although I haven't seen anyone stripping a Leaf pack down to the bare cells, stripping it down to the bare modules (of four cells each) and using your own BMS is practical - check out this for an example:
Leaf module based 150V 65Ah battery pack...
Thank you so much.

Yikes! Battery Management System?! How come this is needed? There was I thinking that at least the battery will be simple enough - a positive here, a negative there and we're done! Clearly not... :(
 

·
Registered
Joined
·
4,752 Posts
I may be able to get hold of a scrap Nissan Leaf. The batteries look easy enough to extract (explained here).
In case it wasn't clear from the article, the title of this article is incorrect: it says that this 16-volt battery is built from six Leaf cells, but it is actually (as correctly described in the article) built from 24 cells in six modules.

Based on a quick scan through the article, it appears that this person - like most people dealing with Leaf components - leaves the modules intact, not breaking them down into individual cells.
 

·
Registered
Joined
·
217 Posts
Thank you so much.

Yikes! Battery Management System?! How come this is needed? There was I thinking that at least the battery will be simple enough - a positive here, a negative there and we're done! Clearly not... :(
Because, from another newbies perspective, from what I gather, not all cells are created equally .

If one cell (or group of parellel cells) in a series pack charges above, or discharges below the predefined values the BMS jumps into action, simplistically bleeding off an overcharging cell , or takes other action as required.

If you bottom balance cells carefully , and limit your charging and discharging to less than maximum reccomended values you may be able to get away without a BMS . ???

I think I need to be further educated on this .
 

·
Administrator
Joined
·
6,104 Posts
My "take" on a BMS

If a cell is going to die - it dies - what you need is a warning that it has died before you end up overcharging the others

I'm using the http://www.evdl.org/pages/battbridge.html
An incredibly simple (even I can understand it) way of finding out if you have lost a cell

I am also periodically checking that my cells are all OK at the top and bottom of my span

With my car I have to unbolt the controller and it's a real pain to check - so I am not doing this very often

If I was smart enough I would have used the Volt BMS system - I would not use any of the non OEM systems because as far as I can tell from this forum they have killed many more batteries than they have saved
 

·
Registered
Joined
·
217 Posts
My "take" on a BMS

If a cell is going to die - it dies - what you need is a warning that it has died before you end up overcharging the others

I'm using the http://www.evdl.org/pages/battbridge.html
An incredibly simple (even I can understand it) way of finding out if you have lost a cell

I am also periodically checking that my cells are all OK at the top and bottom of my span

With my car I have to unbolt the controller and it's a real pain to check - so I am not doing this very often

If I was smart enough I would have used the Volt BMS system - I would not use any of the non OEM systems because as far as I can tell from this forum they have killed many more batteries than they have saved
Doh , the best ideas are always the simplest.
Now Im going to use 46 x Cells instead of my planned 45 so I can evenly split the pack for one of these batt bridges.

So now I'll have 12 cells under each seat in difficult to access enclosures and 22 cells under the hood/bonnet . I could also put a batt bridge on each under seat 12 pack and one on the 22 cell under bonnet pack to tell at a glance if one cell is faulty and from which pack.
 

·
Registered
Joined
·
78 Posts
Discussion Starter #8
Thanks so much for your explanations, guys.

I'm imagining my cells being in a virtually sealed box - those which are slung under the rear tub anyway, so some kind of BMS would seem sensible.

I'm having trouble finding an off-the-shelf BMS. Is there such a thing or do you have to be handy with a soldering iron and know one of a diode from another?
 

·
Registered
Joined
·
1,364 Posts
I'm imagining my cells being in a virtually sealed box - those which are slung under the rear tub anyway, so some kind of BMS would seem sensible
Don't underestimate the impact of getting this wrong... here's what happens when a DIY enthusiast forgets he's running a human BMS :eek:


I'm having trouble finding an off-the-shelf BMS. Is there such a thing or do you have to be handy with a soldering iron and know one of a diode from another?
You're going to get lots of different views here on BMS... but as a novice I'd suggest you select an electronic BMS not one that relies on human interaction. To help narrow down your options start by deciding on your budget because that will help define your battery size/type.

The three projects that I'm working on will use the Tesla BMS controller and Wolf's Leaf BMS controller because I want to use the OEM hardware that was designed for the battery cells that I'm using.
 

·
Registered
Joined
·
217 Posts
Well they don't make it easy for you if you building a pack out of Prismatics

EVWest has no BMS listed on their website
EW Works is Australia only have small BMS that are unsuitable
EVTV have nothing , you think after the fire they would be onto it.

Whats the consensus on Cell modules (AKA Vampire boards ?? )

EG something like http://www.ev-propulsion.com/bms.html
 

·
Registered
Joined
·
78 Posts
Discussion Starter #11
Thanks again for your input, guys.

Looking at off-the-shelf kits in the UK there is no mention of BMSs - except tucked away in the small print.

The home-brew options look beyond my capabilities.

The off-the-shelf BMSs look expensive and bulky - with yet another black box to be taped to the dashboard (?!), but I suppose the alternative is worse.

Would it not be easier and cheaper just to fit thermal cut-outs, perhaps?
 

·
Registered
Joined
·
217 Posts
Ive been tossing up BMS choices & even weather to use one at all, but an Australian unit comes highly recommended, worth a look , the manuals for v2 version are online. New V3 model in the works.

Oh and it will let you hook up your standard LandRover Fuel guage to show Full / Empty battery condition , That for me is a no brainer.

http://zeva.com.au
 

·
Registered
Joined
·
78 Posts
Discussion Starter #13
Oh and it will let you hook up your standard LandRover Fuel guage to show Full / Empty battery condition , That for me is a no brainer.
That's a must-have, although I'd miss the wiggling needle and wildly inaccurate readings in the standard ICE set-up!
 
1 - 13 of 13 Posts
Top